The invention relates to an in the ear hearing aid, comprising a first unit which comprises a microphone, an amplifier, control means for adjusting a parameter of the hearing aid, and a battery compartment, and a second unit which comprises a receiver, the hearing aid further comprising electrical connection means for electrically connecting an output of the amplifier to an input of the receiver, the first and the second unit being accommodated in an earmould whose external shape is substantially adapted to the interior of the ear of the user of the hearing aid and which for this purpose has a substantially tapered shape, viewed in the longitudinal direction of the earmould. Such custom made hearing aids are known, for example from German Gebrauchsmuster 87.13.595. Said document describes a method of manufacturing an earmould.
An impression of the interior of the ear is made. After this, a negative in the form of a molding die is made of this impression. Subsequently, both units are inserted into the molding die via the end of larger cross-section and a liquid plastics is introduced into the molding die. When the plastics has cured the earmould is ready. Thus, both units are encapsulated in the earmould. A disadvantage of such a method is that a replacement of, for example, the receiver is not possible. Moreover, an adaptation to comparatively small ear cavities is not readily possible.
Another method of manufacturing an earmould is to introduce a liquid plastics into the molding die while the two units have not yet been inserted into the molding cavity. After partial curing the plastics which has not yet cured is removed from the molding die. A more or less cured layer of plastics is then left on the wall of the molding die. After complete curing, for example under the influence of heat or under influence of (U.V.) light, the hollow earmould can be removed from the molding die. After a finishing treatment of the untreated earmould the first and second unit can be introduced via the end of larger cross-section. The receiver is introduced first and is slid towards the end of smaller cross-section, where it is secured in the earmould. After this the first unit is mounted in the earmould. This method also has the disadvantage that it cannot readily be adapted to comparatively small ear cavities.